Conventionally, for example, as disclosed below in Patent Literature 1 and Patent Literature 2, a four-wheel drive vehicle that includes an auxiliary transmission to further shift a rotational output shifted by a main transmission is known. This auxiliary transmission generally switches a range between a high-speed range (Hi) and a low-speed range (Lo).
A mechanism that performs this range switch, as disclosed in each Patent Literature, includes a sleeve that is movable along the shaft center of an output shaft of the main transmission. This mechanism switches a power transmission path between a high speed side (a small gear ratio side) and a low speed side (a large gear ratio side) corresponding to a moving position of the sleeve.
Generally, the range switch in the auxiliary transmission is performed in a vehicle stopped state. This is obtained considering a big gear change shock generated by sharply changing the gear ratio in association with the movement of the sleeve in the case where range switch is performed in a vehicle-running state.